Needle roller bearings with a machined outer ring, without an inner ring

are an excellent choice for compact bearing arrangements if the shaft can be hardened and ground (fig. 3)

enable a larger shaft diameter and a stiffer bearing arrangement compared to arrangements with bearings with inner rings

Axial displacement of the shaft relative to the housing is only limited by the width of the raceway on the shaft. By machining the shaft raceways to the appropriate dimensional and geometrical tolerances, it is possible to obtain bearing arrangements with tighter geometrical tolerances. For additional information, refer to Raceways on shafts and in housings.

with D ≤ 17 mm (Fw ≤ 10 mm), are available with non-separable closure rings that act as flanges (fig. 4)
The flanges on larger bearings are an integral part of the outer ring, and the bearings have an annular groove and one or more lubrication holes in the outer ring (fig. 5).

are generally designed as single row bearings, with the exception of RNA 69 (fig. 6) and NA 69 series double row bearings with D ≥ 52 mm (Fw ≥ 40 mm)

The roller and cage assembly and outer ring of a needle roller bearing with flanges form a non-separable unit.

Needle roller bearings with machined rings, without flanges

are separable, i.e. the outer ring, needle roller and cage assembly, and inner ring, can all be mounted separately (fig. 7)
Needle roller and cage assemblies can, depending on the arrangement design, either be mounted:

together with the outer ring

together with the shaft

together with the inner ring

between the outer ring and shaft or inner ring as the final step

However, needle roller and cage assemblies and bearing outer rings must always be kept together as supplied.

are generally designed with one needle roller and cage assembly
However, wide sizes incorporate two needle roller and cage assemblies immediately adjacent to each other and have an annular groove and a lubrication hole in the outer ring (fig. 8).

To accommodate combined radial and axial loads, needle roller bearings with machined rings can be combined with a needle roller thrust bearing with a centring flange, AXW series, if the outside diameter D of the radial bearing is equal to the flange diameter D1 of the thrust bearing (fig. 9, fig. 10).

Sealed bearings

are available in the (R)NA 49 series with a contact seal made of NBR (effective at keeping the lubricant in and contaminants out of the bearing) on one (fig. 11) or both sides (fig. 12)

have an inner ring that is 1 mm wider than the outer ring, which maintains the effectiveness of the seals and simplifies the bearing arrangements even when small axial displacements occur

When capped bearings must operate under certain conditions, such as very high speeds or high temperatures, some grease may leak. For bearing arrangements where this would be detrimental, appropriate actions could be taken.

Associated external seals

can be used for needle roller bearing arrangements (without an inner ring)

Needle roller bearings with one or two seals are supplied greased. They are filled with high-quality grease (table 1) under clean conditions.

The relatively large quantity of grease in the bearings means they can be operated for long periods before relubrication is required (→ Perform calculations). SKF recommends SKF LGWA 2 grease (table 1), if relubrication is required.